There are a lot of online screening tests of symptom lists for adhd. But I do not recommend to trust this kind of "diagnostic tool". ADHD requires a careful clinical examination by a skilled professional with long experience in adhd and comorbid disorders.

Why?

1. ADHD is a lifelong condition. Anyone may experience some symptoms of adhd once in his lifetime. But may not qualify for the whole diagnostic criteria
2. Other persons do not think they have adhd because they think they are just lazy or stupid. This may be part of poor self-observations and impaired judgement
3. Sometimes the adhd symptoms can be confused with other psychiatric disorders or social maladjustment.

So it makes not much sense to try to diagnose adhd without help by a professional (or at least someone familiar with adhd like a skilled adult of a self-help group for adhd).